Cruise controllers are known that allow the speed of the vehicle to be regulated to a driver-selected desired speed. One example of such a control system, which is also known as ACC system (Adaptive Cruise Control), is described in “Adaptive Cruise Control System—Aspects and Development Trends” by Winner, Witte, Uhler and Lichtenberg, Robert Bosch GmbH, in SAE Technical Paper Series 961010, International Congress and Exposition, Detroit, 26–29 Feb. 1996. Since these systems also include a distance sensor, for example in the form of a radar sensor, a stereo camera system or the like, it is possible to regulate the vehicle speed also in such a way that an appropriate safety distance to a vehicle driving ahead is maintained automatically.
However, since a full detection and reliable evaluation of the traffic surroundings is not yet possible with the available sensor systems, these systems are currently suited primarily to relative stable traffic situations such as driving on a highway or expressway. In contrast, in inner-city driving or when driving at low speed on winding roads, the uncertainties in the detection of the individual relevant target object may result in an accident risk. Consequently, known ACC systems are currently designed to allow activation only above a certain limit speed, such as above 40 km/h, for instance.
It has already been proposed to expand the application range of the ACC system to a traffic situation known as stop & go traffic and which occurs with a traffic jam or with slow-moving traffic, for example. This type of traffic situation is relatively stable, too, and thus suited for automatic distance control. However, the functionality must then be expanded in such a way that standing-start and stop processes are also able to be automated.
The speed sensor is currently formed by a system of dynamic wheel-speed sensors, which are already installed in vehicles having anti-lock braking systems or automatic traction control. However, since these wheel-speed sensors can detect the angle increments of the vehicle wheels only with limited resolution, the speed signal becomes unstable and unreliable at low speeds. This is another reason for the control being suspended at low speeds.